Since upgrading to Leopard, I've noticed that some of my Yahoo contacts are showing the user's buddy icon rather than the icon I have assigned to them in my address book. The name is showing up correctly, but not the buddy icon.
Both "use address book images as contacts' icons" and "even if the contact already has a contact icon" are checked in my preferences, and I have tried trashing the preferences and starting over just to make sure.
So far I have only noticed this on a few contacts, all on Yahoo; other contacts are showing the correct behavior. The contacts in question were correctly showing their address book icons before the Leopard upgrade.